Neonatal complications and risk factors associated with assisted vaginal delivery

To investigate neonatal injuries, morbidities and risk factors related to vaginal deliveries. This retrospective, descriptive study identified 3500 patients who underwent vaginal delivery between 2020 and 2022. Demographic data, neonatal injuries, complications arising from vaginal delivery and pertinent risk factors were documented. Neonatal injuries and morbidities were prevalent in cases of assisted vacuum delivery, gestational diabetes mellitus class A2 (GDMA2) and pre-eclampsia with severe features. Caput succedaneum and petechiae were observed in 291/3500 cases (8.31%) and 108/3500 cases (3.09%), respectively. Caput succedaneum was associated with multiparity (adjusted odds ratio [AOR] 0.36, 95% confidence interval [CI] 0.22–0.57, P < 0.001) and assisted vacuum delivery (AOR 5.18, 95% CI 2.60–10.3, P < 0.001). Cephalohaematoma was linked to GDMA2 (AOR 11.3, 95% CI 2.96–43.2, P < 0.001) and assisted vacuum delivery (AOR 16.5, 95% CI 6.71–40.5, P < 0.001). Scalp lacerations correlated with assisted vacuum and forceps deliveries (AOR 6.94, 95% CI 1.85–26.1, P < 0.004; and AOR 10.5, 95% CI 1.08–102.2, P < 0.042, respectively). Neonatal morbidities were associated with preterm delivery (AOR 3.49, 95% CI 1.39–8.72, P = 0.008), night-time delivery (AOR 1.32, 95% CI 1.07–1.63, P = 0.009) and low birth weight (AOR 7.52, 95% CI 3.79–14.9, P < 0.001). Neonatal injuries and morbidities were common in assisted vacuum delivery, maternal GDMA2, pre-eclampsia with severe features, preterm delivery and low birth weight. Cephalohaematoma and scalp lacerations were prevalent in assisted vaginal deliveries. Most morbidities occurred at night. Clinical trial registration: Thai Clinical Trials Registry 20220126004.


Statistical analysis
Demographic data were compiled using descriptive statistics.Categorical data are presented as numbers and percentages, while continuous data are reported as the means ± standard deviations or medians and ranges.We employed PASW Statistics (version 18; SPSS Inc, Chicago, IL, USA) for our statistical analyses.Baseline data (qualitative parameters, maternal complications and infant complications arising from caesarean section) were compared using the chi-squared and Fisher's exact tests.For quantitative variables, the Mann-Whitney U test was employed for univariate analysis, while multiple logistic regression was utilised for multivariate analysis.

Terminology
The following terms were used in this study 6 : • Bruising: this occurs when capillaries rupture, allowing blood cells to seep deep beneath the skin, resulting in the characteristic 'black and blue' marks on the skin.Over time, as the body metabolises the substances in the blood cells, the bruise changes colour, potentially appearing purple, brown, or even green.• Petechiae: this involves bleeding under the skin, characterised by marks resembling a rash of small dots.
Petechiae occurs when tiny blood vessels break open, causing blood to leak into the skin and giving it the appearance of a rash.• Caput succedaneum: this refers to scalp swelling that occurs during labour and is usually evident shortly after delivery.It is commonly associated with prolonged pressure on the fetal head during delivery or a prolonged second stage of labour.• Cephalohaematoma: this condition involves a subperiosteal collection of blood that occurs due to the rupture of vessels beneath the periosteum, typically over the parietal or occipital bone.It presents as swelling that does not cross suture lines.• Subgaleal haematoma: this refers to the accumulation of blood in the loose areolar tissue between the peri- osteum of the skull and the aponeurosis.

Ethics approval and consent to participate
Prior to the commencement of this study, the requisite ethical clearance was procured from the Siriraj Ethics Committee of the Faculty of Medicine, Siriraj Hospital (Si 185/2022).Additionally, this research was registered with the Thai Clinical Trials Registry (20220126004).This study was a retrospective chart review and informed consent was not required.
Caput succedaneum refers to scalp oedema that emerges during labour and typically resolves within 48 h post-birth.This condition commonly presents following prolonged engagement of the fetal head in the birth canal or after vacuum extraction.On the other hand, neonatal jaundice or neonatal hyperbilirubinaemia arises from elevated total serum bilirubin levels.It manifests clinically as a yellowish discolouration of the skin, sclera and mucous membranes.Notably, approximately 60% of term and 80% of preterm newborns exhibit clinical jaundice during their first week post-birth 7 .This manifestation is generally a mild, transient and self-limiting condition that resolves without any intervention and is termed 'physiological jaundice' .Nevertheless, it is crucial to differentiate it from the more severe 'pathological jaundice' to ensure early intervention and prevention of significant complications.www.nature.com/scientificreports/Furthermore, caput succedaneum may give rise to compression-related necrotic lesions, potentially leading to long-term scarring and alopecia 8 .The 'halo scalp ring' is an annular alopecic circle seen in infants after enduring prolonged or challenging labour.This condition arises due to compression from the bony prominences of the maternal pelvis 9 .Instances of infected caput succedaneum are rare 10 .
Bruises and petechiae were the most frequently observed findings in our study.They are generally self-limiting and commonly appear on the presenting portion of the newborn's body.A bruise is a risk factor for the development of hyperbilirubinaemia or jaundice.Hence, it is advisable to closely monitor infants with significant bruising to evaluate the potential development of jaundice 11 .
Our research indicated that assisted deliveries using vacuum or forceps were closely linked to the occurrence of scalp lacerations.Additionally, assisted forceps delivery was notably associated with abrasions and bruises.Assisted vaginal deliveries account for 10-15% of births in Canada 12 , Australia 13 and the United Kingdom 14 .When well-trained physicians conduct such operations, there is a demonstrated association with reduced risks for mothers and newborns [14][15][16] .However, the shift from assisted vaginal deliveries to caesarean deliveries has reduced opportunities for medical professionals to gain expertise in using vacuum and forceps 12,17,18 .Consequently, it is unsurprising that there have been increasing reports of maternal and neonatal trauma related to assisted vaginal deliveries.This has also intensified concerns regarding the comparative safety of using forceps versus vacuum [19][20][21] .
In our study, clavicle fractures accounted for 0.7% (25/3500 cases) of the injuries.These fractures were not significantly linked to assisted vaginal deliveries.According to extensive case series, the incidence of clavicle fractures stemming from birth trauma varies between 0.5 and 1.6% 22,23 .Fractured clavicles often correlate with challenging vaginal deliveries due to factors such as assisted delivery, shoulder dystocia, advanced maternal age, and babies large for their gestational age 22,23 .When a clavicle fracture is identified, it is essential to investigate any concurrent brachial plexus injury.In our dataset, the incidence of brachial plexus injury was 0.1% (4/3500 cases), and all instances resulted from spontaneous vaginal delivery.The only acknowledged risk factor for brachial plexus injury is shoulder dystocia, for which no validated predictive or preventative measures exist.Potential mechanisms leading to neonatal brachial plexus palsy encompass stretching/traction, compression, infiltration and oxygen deprivation 24 ..This association was more pronounced in pregestational diabetes than in gestational diabetes 25 , although the exact cause remains elusive.The suggested mechanisms for this link are fetal hyperglycaemia and hyperinsulinemia, which might heighten neonatal respiratory morbidity, even in vaginal deliveries.
The predominant neonatal morbidities we observed were hypoglycaemia, hypocalcaemia and hyperthermia, which were significantly related to neonatal low birth weight.These findings are consistent with a study by Chand et al. 26 .
Our research indicated that neonatal birth injuries were significantly correlated with preterm delivery, assisted vaginal deliveries, and babies large for their gestational age.Previous research found that the risk of birth injury was double for infants weighing between 4000 and 4499 g compared to those of average birth weight.The risk www.nature.com/scientificreports/ was threefold for infants weighing between 4500 and 4999 g and surged to 4.5 times for those weighing more than 5000 g 27 .Another study found a 7.7% incidence of fetal injury in infants weighing over 4500 g 28 .Other studies have emphasised that preterm infants are particularly prone to respiratory complications due to their premature birth, a finding consistent with our observations 29 .Maternal obesity, defined by a body mass index of > 40 kg/m 2 , increases the risk of birth injuries.This group of parturients often has higher rates of assisted vaginal delivery and an elevated risk of bearing a large-forgestational-age infant, which can further raise the likelihood of shoulder dystocia 30 .However, our study did not observe a significant incidence of brachial plexus injury.
Interestingly, our findings highlight a significant occurrence of neonatal injuries and morbidities after regular hospital (daytime) hours.US and Austrian national studies indicate that there are heightened risks for adverse maternal and neonatal outcomes during night deliveries [31][32][33] .However, Yee et al. noted that academic medical centres equipped with round-the-clock specialists produced similar outcomes for pregnant women with postpartum haemorrhage, regardless of the delivery time 34 .Continuous in-house staffing in obstetric units might, therefore, enhance night-time outcomes.

Implications for clinical practice
In our study, we observed a high incidence of neonatal morbidities and complications, underscoring the importance of healthcare practitioners prioritizing vigilant monitoring of newborns delivered vaginally, particularly those born through assisted methods like vacuum or forceps.Early detection and management of complications such as neonatal jaundice and caput succedaneum are crucial in preventing long-term sequelae.
The study emphasized the significance of ensuring healthcare professionals receive sufficient training and maintain expertise in conducting assisted vaginal deliveries.Continuous education and simulation training are essential for sustaining proficiency in utilizing vacuum and forceps, thus reducing the risks of maternal and neonatal trauma linked with these procedures.
Our research highlights the crucial need for healthcare professionals to receive adequate training and experience in conducting assisted vaginal deliveries.Continuous education and simulation training are vital in maintaining proficiency with vacuum and forceps, thus reducing the risks of maternal and neonatal trauma associated with these procedures.The notable incidence of neonatal injuries and morbidities following regular hospital hours underscores the necessity of continuous in-house staffing in obstetric units.This staffing approach could enhance outcomes during nighttime deliveries, guaranteeing prompt access to specialized care as necessary.

Limitations of the study
Our study's reliance on retrospective data from medical records may introduce bias due to incomplete documentation or variations in reporting practices across different healthcare facilities.Additionally, the retrospective nature of the study limits our ability to establish causality between maternal and neonatal factors and the observed complications.The findings of our study may not be generalizable to populations outside of the study setting or to different healthcare systems with varying practices regarding vaginal deliveries and neonatal care.

Gaps in existing literature and implications for future research
Future research could further explore the comparative safety and efficacy of vacuum versus forceps-assisted vaginal deliveries, specifically focusing on neonatal outcomes and maternal morbidity.Longitudinal studies with larger sample sizes are necessary to offer more robust evidence in this domain.
Further investigation into additional maternal and neonatal factors, such as maternal obesity, maternal age, and birth order, could yield valuable insights into neonatal complications and risk factors.This deeper understanding could aid in risk stratification and the development of targeted interventions to mitigate adverse outcomes.
Additional research is needed to investigate the effects of delivery timing, including daytime versus nighttime deliveries, on neonatal outcomes and maternal health.Prospective studies with standardized data collection protocols and comprehensive risk adjustment are warranted to better comprehend the factors influencing outcomes during various times of the day.

Conclusions
Neonatal injuries and morbidities were frequently observed in cases involving assisted vacuum delivery, maternal GDMA2, severe-feature pre-eclampsia, maternal anaemia, preterm delivery, and low birth weight.These morbidities were often associated with factors such as a prolonged second stage of labour, fetal distress, maternal obesity, and infants being large for their gestational age.Notably, most of these morbidities manifested during night-time.

Table 1 .
1, Relationship between neonatal injuries, morbidities and types of vaginal delivery (univariate analysis).

Table 2 .
Overview of neonatal injuries and morbidities following vaginal delivery (multiple complications possible).

Table 3 .
Relationship between neonatal injuries, morbidities and maternal parity (univariate analysis).Fetal asphyxia was significantly associated with mothers having GDMA2 in our research, corroborating the findings byKawakita et al.

Table 4 .
Correlation of neonatal injuries and morbidities with maternal diabetes mellitus and hypertension (univariate analysis).

Table 5 .
Correlation of neonatal injuries and morbidities with gestational age at the time of delivery (univariate analysis).

Table 6 .
Association of neonatal injuries and morbidities with prolonged second stage of labour and fetal distress (univariate analysis).By addressing these limitations and suggesting avenues for future research, the contribution to the ongoing efforts to improve maternal and neonatal care and reduce the incidence of complications associated with vaginal deliveries.

Table 7 .
Association of neonatal injuries and morbidities with maternal anaemia and neonatal birth weight (univariate analysis).